These efforts cover both basic and applied aspects of mycoplasmas and related wall-free prokaryotes, including their neurotoxins, enzymes and other biological factors involved in virulence, their immunological interrelationships, and their possible role in human disease or in diseases of uncertain etiology. Current projects of interest concern the characterization of a new group of pathogenic spiroplasmas and sero-epidemiological studies on the human exposure to these new microbial forms. Development of an effective culture medium for the recovery and propagation of these organisms from host tissues has also provided a more effective medium for recovery of Mycoplasma pneumoniae from human tissues and washings, and for propagation of other fastidious mycoplasmas. BIBLIOGRAPHIC REFERENCES: Tully, J.G., Whitcomb, R.F., Clark, H.F., and Williamson, D.L.: Pathogenic mycoplasmas: cultivation and vertebrate pathogenicity of a new spiroplasma. Science 195: 829-894, 1977. Tully, J.G., and Razin, S.: The Mollicutes (mycoplasmas). In Laskin, A.I., and Lechevalier, H.A. (eds.): Handbook of Microbiology, 2nd edition, Cleveland, Chemical Rubber Co., 1977, volume 1 (in press).